A laser micrometer provides dimensional information about objects placed in the path of a sheet of laser light which is detected by, or scanned across, a detector. The width of the “shadow” created on the detector provides a dimension of the object.
Existing “laser micrometers” are typically designed for small objects, with a maximum dimension of 6 inches. However, laser micrometers offer accuracy better than 1/1000th of an inch, at a scan rate of up to a thousand samples per second. A “sample” refers to a readout of the complete detector array providing one or more measurements of the object(s) within the micrometer.
In a laser micrometer, a laser light sheet is usually formed using either static refractive lens elements or a rotating mirror to scan the beam. The limitation on maximum size is a limitation on the size of these light sheet forming elements.
Alternative systems, known as “light curtains” are usually used in applications such as safety monitoring for preventing access to hazardous or secured areas. However, a laser curtain can be adapted to provide measurements of approximately ⅛th of an inch accuracy and resolution. The scan rate from a light curtain is typically 100-200 samples per second.
In a light curtain system, that light sheet is typically a series of independent light beams emitted from a linear array of light emitting diodes (LEDs) spaced at the desired measurement resolution. An array of matching photodiode detectors completes the system. The light curtain design is limited in resolution by the physical spacing between the LEDs. The maximum scan rate is limited by the need to strobe the LEDs in segments to avoid crosstalk arising from adjacent photodiodes “seeing” the wrong LED. The maximum scan rate is also reduced as the size of the light curtain increase due to the large amount of data produced and the limitations of the typical interface and data encoding scheme.
Therefore, there is a need for a large format, high speed laser micrometer that is capable of scanning large objects with a high scan rate and high degree of accuracy.
It is an object of this invention to provide a large format, high speed laser micrometer to scan large objects with a high scan rate and a high degree of accuracy. It is an additional object of this invention to provide a parabolic mirror assembly for forming a collimated laser light sheet.